The mechanism by which cytochrome c transfers electrons will be investigated from a chemical point of view. The surface location(s) of the entry and exit of the electron will be established by comparing the chemical reactivity of selected surface residues of cytochrome alone and when complexed with cytochrome oxidase, cytochrome peroxidase, cytochrome oxidoreductase and ferrohexacyanide, all of which form stable complexes. Perturbation of the conformation of cytochrome by complexation will be investigated. Proposed pathways between the exterior of cytochrome c and its buried heme iron will be tested using proteins containing unnatural amino acid replacements designed to perturb electron transport with minimal conformational distortion. These chemical mutant proteins will be made by reconstitution of cytochrome c from appropriate mixtures of synthetic and naturally occuring peptides. Conversely, amino acid replacements will also be designed to specifically perturb various internal features of cytochrome c to investigate their role in the folding of the polypeptide and in the stability of the globular conformation.